Lower glycols, i.e., monoethylene glycol 1,2-propylene glycol and 1,3 propanediol, find a plurality of uses as operative fluids, e.g., antifreezes, deicers, heat transfer fluids, quenchants, brake fluids and other hydraulic fluids, lubricants, absorbents, and solvents. Operation fluids are thus characterized as fluids which are used to perform a function. In the context of performing this function, they are subjected to inclusion of impurities and/or degradation. For instance, an antifreeze composition for an internal combustion engine may not only be subject to heat, but also to the various materials of construction of the cooling system as well as dirt, combustion gases in the event of leaky heat gaskets, and the like.
Often operative fluids contain corrosion inhibitors, buffers, antioxidants and/or other adjuvants to make them suitable for use in process equipment. These adjuvants may be consumed or removed from the fluid during use. Contamination of the fluids may also occur during use or storage, and the fluids, especially those subjected to elevated temperatures, may degrade. The degradation products may be deleterious in the process equipment in which the operative fluid is used. With the loss of the adjuvant effectiveness or upon contamination or upon the generation of undue amounts of degradation products, the operative fluid may become unacceptable for its intended use.
When the operative fluid becomes unacceptable for its intended use, the fluid has frequently been disposed. Not only does this entail a loss of lower glycol values, but, also, care should be taken to assure that the manner of disposal of the fluid is environmentally acceptable. Alternatively, the lower glycol could be recovered from the operative fluid for reuse. Separation processes, such as distillation of spent solvents, can prove to be energy intensive. See, for instance, Chemical Abstracts, Vol. 111 (20); 177607 q, summarizing Shub, et al., "Utilization of Used Antifreeze", Khim, Tekhnol. Topl. Masel (8), 16-18 (1989); U.S. Pat. No. 4,225,394; Chemical Abstracts, Vol. 101(4); 25944 c, summarizing Hungarian patent publication 29752, Feb. 28, 1984; and Chemical Abstracts, Vol. 104 (22): 189629 s, summarizing Wehner, et al., "Processing of Residues from Solvent Regeneration for Selective Separation Processes", East German patent number 226557, Aug. 28, 1985.
U.S. Pat. No. 4,427,507 discloses an electrodialysis system for recovering ethylene glycol from aqueous purge streams for ethylene oxide plants. The patentees state:
"Finally, the process according to the invention might also be used in the regeneration of glycol-water antifreeze mixtures for instance for motor cars." (Column 4, lines 13 to 15)
No example or statement relating to the effectiveness of electrodialysis for recovery of ethylene glycol from antifreeze mixtures is given. In view of the inability of electrodialysis to effect separation of non-charged components such as colloidal metals and organic contaminants, the viability of electrodialysis as an effective means to recover glycol from antifreeze mixtures is placed into question. Chemical Abstracts, Vol. 104 (20): 170054d, reporting on Japanese patent application Kokai 60/216884, Oct. 30, 1985, relates that electrodialysis has been proposed to treat waste water from polyester fiber manufacturing. No disclosure or suggestion of the use of electrodialysis for recovery of ethylene glycol from antifreeze is reported.
British patent specification No. 1,463,324 discloses the use of semi-permeable membranes for the recovery of ethylene glycol from waste water for ethylene oxide processes. A commercial polyamide membrane made by duPont was the only specified membrane and membrane material.
Grunwald's Czech patent application 87/01681 is reported by Derwent, 88-315268/45, to disclose waste antifreeze regeneration by removing mechanical impurities, passing the material through cation exchanger and adding ethylene or propylene glycol.
As another alternative to the recovery of lower glycol, operative fluid for some applications can be analyzed, and appropriate adjuvants in appropriate amounts can be added to the operative fluids to replenish adjuvants or counter at least some of the effects of degradation products or contaminants. This procedure is frequently not practical except in large scale industrial applications. Without an analysis, a risk exists that too much or too little of the adjuvant or that an improper adjuvant may be added to the fluid. In such an event, the deleterious properties of the operative fluid may not be sufficiently ameliorated, and even may be exacerbated, by the improper concentrations of adjuvants. Moreover, the presence of contaminants is not addressed by the addition of adjuvants.
Accordingly, processes are sought which can effectively reclaim lower glycol from operative fluids such that deleterious contaminants and degradation products, whether or not ionic, can be removed and such that any adjuvants, whether in active or consumed form, can be removed. The reclaimed lower glycol can then, for instance, be reused as an operative fluid and a standard adjuvant package added without the need for analysis. Advantageously, the processes would be economical, require little energy consumption and be reliable.
The benefits of such processes would not only be perceptible for industrial applications such as heat transfer fluids, quenchants and absorbents, but also would apply to small applications such as local processing of used automotive antifreeze. Further, the processes may be viable for deicing utilities such as for aircraft and airport runways where on-site processing of intermittent, large quantities of operative fluid is sought.